In a solid-state imaging element, a plurality of pixels are arranged. Thus, for preventing color mixture, photoelectric converters forming adjacent pixels need to be separated, and various proposals have been made for such a demand.
For example, Patent Document 1 proposes that a separation structure is formed before formation of photodiodes and a P-type impurity is diffused on a trench surface by a solid-phase diffusion technique to form a P-type diffusion layer.
Moreover, Patent Document 2 proposes that a trench is formed from a light receiving surface side and pixels are separated together with a P-type impurity between photodiodes.
Further, Patent Document 3 proposes that a trench is formed at the periphery of a photodiode and a PN joint is formed at a side wall of the trench. In this manner, an electric field of a peripheral portion is intensified, and a saturated charge amount Qs is increased. A P-type impurity layer is formed by ion implantation or solid-phase diffusion, and an N-type impurity layer is formed by ion implantation.